Increased SPARC expression in primary angle closure glaucoma iris.
OBJECTIVE
SPARC (secreted protein, acidic, and rich in cysteine) is involved in extracellular matrix (ECM) organization. The purpose of this study was to evaluate the expression of SPARC in iris tissue from primary angle closure glaucoma (PACG) eyes.


METHODS
Iris tissue was obtained from peripheral iridectomies performed during trabeculectomy surgery in nine PACG and 16 primary open-angle glaucoma (POAG) eyes at the Singapore National Eye Centre. Three non-glaucoma control iris specimens were obtained from patients who underwent Descemet's stripping automated endothelial keratoplasty (DSAEK) procedure. SPARC and collagen I expression were quantified by real-time polymerase chain reaction (PCR). The histological distribution of collagen I and III in the iris stroma was determined using picrosirius red polarization. Density of the iris stromal vasculature was also calculated.


RESULTS
The mean age was 68.9+/-10.9 years and 65.7+/-12.2 years in POAG and PACG groups, respectively. The PACG iris expressed SPARC 13.6-fold more and collagen I 5.2 fold more compared to non-glaucoma control iris. The PACG iris also demonstrated 3.3 fold higher SPARC and 2.0 fold higher collagen I expression relative to the POAG iris. The density of collagen I was greater in PACG eyes than in POAG and control eyes (p<0.001). The mean density of iris stromal blood vessels per micron square area was similar in all three groups.


CONCLUSIONS
SPARC was significantly increased in the PACG iris. The data suggest that SPARC could play a role in the development of PACG by influencing the biomechanical properties of the iris through a change in ECM organization.
Chua
Jocelyn
J
Singapore National Eye Centre, Singapore.
Seet
Li Fong
LF
Jiang
Yuzhen
Y
Su
Roseline
R
Htoon
Hla Myint
HM
Charlton
Amanda
A
Aung
Tin
T
Wong
Tina T
TT
D000368:Aged; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D003710:Demography; D005260:Female; D005786:Gene Expression Regulation; D015812:Glaucoma, Angle-Closure / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007498:Iris / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D015676:Osteonectin / Q000235:genetics / Q000378:metabolism*; D011300:Preoperative Care; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000473:pathology
D024042:Collagen Type I; D015676:Osteonectin; D012333:RNA, Messenger